Considering that bioavailability is related to solubility (Xiangdong et al., 2000), the bioavailability of metal decreases in the order of exchangeable > acid reduction > organic > residual forms. Among the studied metals, Cd (17–53%) showed the highest proportion in the sedimentary fraction. The metals in sediment at the residual phase represents largely embedded in the crystal lattice of sediment (Yuan et al., 2004).